1. Field of the Invention
The present invention relates to an irrigation control system. More particularly, the invention relates to a peer-to-peer irrigation sprinkler control system with the ability to monitor and control the entire system from any satellite controller.
2. Description of the Related Art
In the area of irrigation management and control, there are two significant types of control systems that are used: the stand-alone controller and the central-satellite system. FIG. 1 shows a traditional stand-alone controller 1, which is typically used for smaller irrigation sites, with outputs varying from four (4) to approximately forty eight (48) outputs. The stand-alone controller 1 is a device that is usually wall mounted, and offers a user interface such as a keypad and a liquid crystal display. With the user interface, a user can set up automatic watering programs, perform manual watering, as well as perform some additional functions for irrigation control.
Connected to the stand-alone controllers 1 are sensors 3 and irrigation solenoid valves 5. The sensors 3 monitor multiple variables that typically include the amount of rainfall, water flow and power consumption. Then, the sensors 3 provide this data to the stand-alone controller 1. Also connected to the stand-alone controller 1 are a plurality of valves 5. The valves 5 are typically 24 VAC solenoid operated valves. The valves 5 are connected to the stand-alone controller 1 with field wiring 7 that delivers the 24 VAC to the valve solenoid.
The stand-alone controller 1 provides valve control and records sensor data as input to various programmable features. The controllers 1 are set-up and programmed via a graphical user interface on the controller. It is known in the art that typical irrigation controllers contain microprocessors as disclosed in U.S. Pat. No. 5,956,248, by Williams et al.
In larger installations, multiple stand-alone controllers must be used because the distance between the controller and valve stations is limited by a maximum amount of tolerable wiring impedance. However, sites that utilize multiple stand-alone controllers are difficult to maintain because they must be managed independently at the location of the installation.
An alternative to the multiple stand-alone controllers solution for large installations is a conventional central-satellite control system shown for example in FIG. 2. U.S. Pat. No. 4,244,022 entitled “Irrigation Control System” by Kendall, discloses a master-slave type control system for large-scale irrigation that incorporates a central computer 9 connected to a plurality of satellite controllers 11 which are in turn connected to control irrigation solenoid valves. Central-satellite control systems generally consist of various sense and/or control devices linked together via a communication bus 13. This distributed control methodology allows the management of large sites from a single location. A typical installation will contain multiple field controllers, or satellites 11, and a single central control center 9. The central control center is managed by a personal computer 9.
The satellite controller 11 is a field device, similar to a stand-alone controller, that offers both valve solenoid control and various sensor interfaces. More sophisticated satellites also have a user interface for local programming.
A major difference between the satellite controller 11 and the stand-alone controller 1 is the communication bus 13 interface. The communication bus 13 interface allows the satellites 11 to communicate with the remote central computer 9. The type of communication bus 13 varies depending on the requirements of each individual site. Typical central-satellite systems use twisted pair wire, radio modems, analog telephone modems, wireless communication (RF VHF, UHF, microwave frequencies), fiber optics, power lines, telephone cables, cellular telephones, infrared, wireless pager systems, or television cables for the communication bus.
In managing large installations, the central-satellite system has some advantages over using multiple stand-alone controllers. The central-satellite system significantly reduces the manpower and level of effort required to maintain a large installation. For example, problems at a satellite location can be instantly reported to the central computer. Also, complex watering schedules can be realized, such as those based on evapotranspiration, by utilizing the computer's graphical user interface and processor capabilities. U.S. Pat. No. 5,208,855 by Marian, discloses one such method and apparatus for irrigation control using evapotranspiration. U.S. Pat. No. 5,870,302 by Oliver discloses a system and method for using evapotranspiration in controlling automated and semi-automated irrigation systems.
Despite the advantages of the central-satellite system, problems still exist with this system. The cost of a central-satellite system can be very high. For example in a smaller site consisting of 5-10 satellite controllers, the costs associated with operating and maintaining a central computer are not feasible, even though a networked solution is preferred. Additionally, there is a large and difficult learning curve for a system operator to fully understand and utilize the capabilities of the system. Moreover, the satellites are mostly simple receivers that can only communicate on the bus when specifically addressed by the central computer.
The Oliver patent discloses that satellite controllers may communicate with other satellite controllers but only to pass data along from a communications and electronic control device. The Oliver patent does not disclose satellite controllers that are capable of monitoring and controlling the entire irrigation control system. Similarly, U.S. Pat. No. 5,740,031 by Gagnon, discloses irrigation controllers that can transmit and receive communications with other irrigation controllers and computer interfaces but in the capacity of a repeater when the central computer can not communicate directly with a controller due to signal attenuation and/or reflection. Again, Gangon does not disclose an irrigation controller capable of monitoring and controlling the entire system. If the central computer fails, then the entire system must operate as individual stand-alone controllers. The present invention provides a system, method and apparatus to meet these needs and address these deficiencies.